Tailoring a bidirectional negative stiffness (BNS) structure with mechanical diodes for mechanical metamaterial structures

A new structure with a bidirectional negative stiffness (BNS) value utilizing buckling phenomena (often called bi-stable or snap-through) and a mechanical diode are presented with regard to mechanical metamaterial applications. The need for cost and mass efficient vibration isolation parts within the modern aerospace, automotive, and civil industries has been the subject of many interesting studies in the last several decades. With conventional materials in nature, many innovative approaches have been proposed, but with some limitations for vibration suppression. To cope with these difficulties, it was possible to employ a man-made material with a negative density or negative stiffness, not existing in nature. Recently metamaterials, i.e., man-made repeating structures with negative densities or/and stiffness values, have been proposed and their applications have been reported. This research presents a new man-made structure with a BNS, using the help of bi-stable mechanisms and a mechanical diode. With regard to the metamaterial application of this phenomenon, the dispersion nature of a 1D bi-stable mechanism has been studied and a new novel structure having BNS with a mechanical diode is presented. The effects of states of snap-through were highlighted and quantified experimentally.